Formation of Multiple Basins above Low Angle Detachments; A Centrifuge-Model Approach

Abstract

Extended scaled centrifuge models, simulating lithospheric deformation, show that depocenters of sedimentary basins, formed above lithospheric detachment zones, migrate both in space and time. If associated with a low-angle mantle detachment, this migration results in formation of multiple basins from a single phase of model extension. Unlike the multiple detachment model proposed for formation of multiple basins or models invoking transtensional deformation, the current analogue models suggest that multiple basins may form due to continuous displacement along one single low-angle detachment during orthogonal rifting. Model results suggest that the geometry and location of sedimentary basins are strongly dependent on the coupling between the upper crust and mantle lithosphere by the ductile lower crust, and the dip of the prescribed “fault/shear zone” in the mantle lithosphere. Steeply dipping lithospheric detachment enhances coupling and hence formation of a single basin in the upper crust above the maximum asthenospheric upwelling in the centre of the rift. In contrast, low-angle detachment in the lithosphere promotes decoupling of the upper crust and any resulting basins from the underlying mantle lithosphere. The dip angle of the mantle detachment affects both location and geometry of the basin. A low-angle shear zone in the mantle lithosphere decouples the broad sag in the upper crust, whereas a steep shear zone promotes coupling and initiates narrow, but deep basins.